London, England (CNN) -- British Prime Minister Gordon Brown is denying allegations of "abusive behavior" and "volcanic eruptions of foul temper" ahead of the publication of a new book by a top British political journalist.

The claims come in a book by Andrew Rawnsley of the Observer newspaper, which will be released March 1. The newspaper began running excerpts on Sunday.

"These malicious allegations are totally without foundation," Brown's official spokesman said in a statement Saturday. The spokesman is traditionally not quoted by name.

The Observer claimed that Brown's behavior upset staff at his office, 10 Downing Street, so much so that the head of the civil service launched an investigation and "ordered" the prime minister "to change his behavior."

Britain has a professional civil service which runs the administration of the government, distinct from elected politicians.

The Cabinet Office, a part of the civil service, issued a strongly-worded denial that Sir Gus O'Donnell had looked into Brown's behavior or warned him about it.

"It is categorically not the case that the Cabinet secretary asked for an investigation of the (prime minister's) treatment of Number 10 staff," his office said in a statement. "These assertions have been put to the Cabinet secretary who has rejected them."

Before the publication of the excerpts from the book, there were rumors it would allege that Brown had hit staffers, which he denied Saturday.

"Let me just say, absolutely clearly, so that there is no misunderstanding about that: I have never, never hit anybody in my life," he said, according to a statement from his office.

The book, "The End of the Party," apparently does not claim the prime minister hit people.

Brown is required by law to call an election by June this year. The date has not yet been announced, but it is widely expected to be May 6, and the election campaign has already started.

One of the top strategists in Brown's Labour Party, Peter Mandelson, declined to deny that Brown had a temper, but painted his personality as a virtue.

"I don't think he so much bullies people as he's very demanding of people. He's demanding of himself, he's demanding of people around him," Mandelson said on the BBC's "Andrew Marr Show" on Sunday.

"He does not like taking no for an answer.... there is a degree of impatience about the man, but what would you like? Some sort of shrinking violet at the helm of the government?" Mandelson asked.

Mandelson laughed and dodged a question from Marr about whether Brown had ever hit him or shouted at him.

But he said Rawnsley had a history of writing about events he had not witnessed.